Saturn V “moon rocket” engine firing again after 40 years, sort of

NASA continues to push forward with the design of its new heavy lift rocket, the Space Launch System. With the cancellation of the Constellation Program, SLS is NASA's planned heavy launch vehicle at the moment. While commercial entities continue to tackle the problem of moving payloads and crews to low Earth orbit, SLS is intended to replace the Space Shuttle as a heavy lift platform for shifting large cargoes into low Earth orbit and points beyond.

If SLS is ever to actually fly, it will require a tremendously powerful set of engines to get it off the ground. Perennial launch contract winner ATK is sure to get in on the action, supplying solid rocket boosters to the launch stack. But a powerful liquid-fueled engine is required as well. There are many candidates and design options, but NASA is actually turning its gaze a bit toward the past for inspiration.

The largest and most powerful rocket to successfully lift off was the Saturn V, which flew men and equipment to the Moon as part of Project Apollo in the 1960s and 1970s. The rocket's first stage had a lot of lifting to do, so it boasted the largest and most powerful liquid-fueled rocket engines to ever fly: the Rocketdyne F-1. Producing 1,500,000 pounds of thrust at sea level and consuming one ton of refined kerosene (RP-1) and two tons of liquid oxygen per second, the Saturn was propelled skyward on five of these monstrous engines.

Enlarge/ Modern engineers in 1960s engineer dress cluster around an F-1. The Russian RD-170 produced more power but isn't really a single engine.

The F-1 is a gas-generator cycle rocket engine, burning a bit of fuel outside the combustion chamber to power the pumps of the engine. Earlier today, NASA test fired an F-1 engine's gas generator segment at the Marshall Space Flight Center in Alabama. This is the second F-1 gas generator firing this year; an earlier test took place on January 10.

The process for test-firing a 40+ year-old rocket engine, even if it's just the gas generator segment, is complicated: no current launch vehicles use the engine, so it wasn't a matter of simply grabbing one from a warehouse somewhere. Engineers removed components from an F-1 engine in storage at MSFC, as well as from another in "pristine" condition at the Smithsonian National Air and Space Museum in Washington, and then laser-scanned them using a structured light 3D scanner. Once this had been done, new gas generator parts were fabricated from the scans.

The gas generator itself was no slouch, producing about 31,000 pounds of thrust when lit. In the full-up engine, this thrust was used to drive a turbine that produced about 55,000 bhp, which in turn drove the turbopumps that kept the thirsty engine fed with the three tons per second of RP-1 and LOx.

A redesigned version of the F-1 engine itself almost certainly won't be used for SLS, but there's still a huge amount of value in studying the old engine's design. "This effort provided NASA with an affordable way to explore an engine design in the early development phase of the SLS program," said Chris Crumbly, manager of the SLS Advanced Development Office.

The Space Shuttle Main Engines are far more efficient beasts than the venerable F-1—in addition to being reusable, they're staged combustion engines, reclaiming and combusting their exhaust gasses. However, these engines are also tremendously complex compared to the F-1 design, and they are too expensive to use in single-use applications like SLS. The F-1 is a proven design, and by measuring exactly how it worked, it can be improved upon.

"Modern instrumentation, testing and analysis improvements learned over 40 years, and digital scanning and imagery techniques are allowing us to obtain baseline data on performance and combustion stability," noted Nick Case, an engineer working at Marshall's Propulsion Systems Department. He even indicated the modern-day test stand instrumentation was gathering data not collected when the engine was originally being checked out in the 1960s.

NASA will continue testing on reconstructed F-1 components to gain more insight into the giant engine's functional parameters. The testing will ultimately culminate in combined test of a reconstructed F-1 "powerpack" that will include the gas generator and turbopump.

Lee Hutchinson
Lee is the Senior Technology Editor at Ars and oversees gadget, automotive, IT, and culture content. He also knows stuff about enterprise storage, security, and manned space flight. Lee is based in Houston, TX. Emaillee.hutchinson@arstechnica.com//Twitter@Lee_Ars

174 Reader Comments

Will the new instrumentation and analysis help to really find out how to make the F1 engine immune to combustion instability? AFAIK, that problem was originally licked by throwing all permutations of injectors they could think of at the test stand and finding out the one that didn't blow up, meaning, sheer luck.

Also, where do you get off not considering the RD-170 a single engine? Had the aforementioned sheer blind stroke of luck not happened to the Huntsville engineers, the F1 would've had to have several combustion chambers as well. One turbomachinery=one engine.

Glad to see proven technology like this being used as the basis for further enhancement. Drives me crazy when perfectly good tech is ignored in favor of starting from scratch. That has its place, but for something like this it would be foolish to bypass it.

On a side note... 1,500,000 freakin' POUNDS of thrust at sea-level for just ONE F-1... Zoiks!

Pratt&Whitney-Rocketdyne seems to be also seriously looking at the F1, as an engine for advanced liquid-fueled boosters for the Block 1b and later versions of the SLS. They reckon that by using two of them per booster, four in total, to replace their shuttle-derived five-segment SRBs, they can deliver about 15% more payload more reliably and less expensively than other options, perhaps even removing the need for a Block 2 SLS design. Of course, ATK has their own advanced booster plans for their solid booster technology, so time will tell.

It's interesting how much interest these engines are getting, considering their low performance (in efficiency terms; a low chamber pressure leads to a low specific impulse). Given what NASA's been through with STS program, I can't blame them for looking for reliability and cost over pure performance. Though, the logical modern iteration of the F1 would hopefully be brought up to date with a higher combustion chamber pressure. PWR was developing that engine, the F-1A, when the Apollo program was cancelled, but perhaps a good idea never dies.

Will the new instrumentation and analysis help to really find out how to make the F1 engine immune to combustion instability? AFAIK, that problem was originally licked by throwing all permutations of injectors they could think of at the test stand and finding out the one that didn't blow up, meaning, sheer luck.

It makes me happy to know that the same technique I used for stress testing problems was used to propel astronauts to the moon.

A redesigned version of the F-1 engine itself almost certainly won't be used for SLS,

What makes you so certain?

marcusj0015 wrote:

Why does it have to eat through SO much fuel though, and putting out SO much carbon? I know I know, it's a pipe dream to want a green Rocket, but I do, and I'mma try to armchair work on it. :c

Define "SO much". At two launches per year, a Saturn V would consume 1,540,000 liters of RP1 (essentially kerosene, and not appreciably different than jet fuel). That's about the same as 5 A380 airliners fully fueled.

Pretty fricken remarkable isn't it? Designed 50 years ago, no less. Saturn V happens to be the only booster in history with a flawless launch record. Although it was with a bit of luck as they had their problems, as tigas outlined. They had issues with POGO oscillations on practically every mission.

3 tons of fuel and oxidizer per second? It makes my F100-229 look puny: 29,000 lbs of thrust and mere ~1000 pounds of fuel per minute (in full AB).

Why does it have to eat through SO much fuel though, and putting out SO much carbon? I know I know, it's a pipe dream to want a green Rocket, but I do, and I'mma try to armchair work on it. :c

You can very easily make a "green" rocket. Instead of burning kerosene, burn liquid hydrogen. The exhaust gasses are just water. The Space Shuttle Main Engines did this, as do many others, though typically as an upper stage or a core sustainer with solid boosters. The Delta IV is the only large rocket that has a purely hydrogen/oxygen first stage.

The reason you use kerosene instead of hydrogen for the first stage is that the RP1 gives you a higher specific thrust (more lifting power) while the LH2 gives you a higher specific impulse (better efficiency). You want the high thrust to get the rocket off the ground and out of the thickest part of the atmosphere quickly, while at higher altitudes and speeds the thrust-to-weight ratio is less critical and efficiency more so.

Engineers removed components from an F-1 engine in storage at MSFC, as well as from another in "pristine" condition at the Smithsonian National Air and Space Museum in Washington, and then laser-scanned them using a structured light 3D scanner. Once this had been done, new gas generator parts were fabricated from the scans.

This part puzzled me. I always assumed there was a filing cabinet somewhere, at NASA HQ or elsewhere, with the blueprints for all their past constructions, so it's weird to me that the engineers here had to measure the parts needed in order to manufacture replacements. After the inevitable apocalypse/rapture the left behind will rely on a repository of instructions to rebuild machines common to us today, tractors, bulldozers, gas-generator cycle rocket engines. Is that not going to happen?

Engineers removed components from an F-1 engine in storage at MSFC, as well as from another in "pristine" condition at the Smithsonian National Air and Space Museum in Washington, and then laser-scanned them using a structured light 3D scanner. Once this had been done, new gas generator parts were fabricated from the scans.

This part puzzled me. I always assumed there was a filing cabinet somewhere, at NASA HQ or elsewhere, with the blueprints for all their past constructions, so it's weird to me that the engineers here had to measure the parts needed in order to manufacture replacements. After the inevitable apocalypse/rapture the left behind will rely on a repository of instructions to rebuild machines common to us today, tractors, bulldozers, gas-generator cycle rocket engines. Is that not going to happen?

There is nothing close to a complete set of “Saturn blueprints” in federal archives. I have also been to the archives at Kennedy Space Center, Marshall Space Flight Center, Houston, and Fort Worth. There is nothing approaching a “complete set of Saturn 5 blueprints” anywhere.

But then, there never was a complete set of the technical documentation.

Engineers removed components from an F-1 engine in storage at MSFC, as well as from another in "pristine" condition at the Smithsonian National Air and Space Museum in Washington, and then laser-scanned them using a structured light 3D scanner. Once this had been done, new gas generator parts were fabricated from the scans.

This part puzzled me. I always assumed there was a filing cabinet somewhere, at NASA HQ or elsewhere, with the blueprints for all their past constructions, so it's weird to me that the engineers here had to measure the parts needed in order to manufacture replacements. After the inevitable apocalypse/rapture the left behind will rely on a repository of instructions to rebuild machines common to us today, tractors, bulldozers, gas-generator cycle rocket engines. Is that not going to happen?

There is nothing close to a complete set of “Saturn blueprints” in federal archives. I have also been to the archives at Kennedy Space Center, Marshall Space Flight Center, Houston, and Fort Worth. There is nothing approaching a “complete set of Saturn 5 blueprints” anywhere.

But then, there never was a complete set of the technical documentation.

I think that's the point he's getting at. Why isn't there a set of blueprints for something like this? It seems like common sense that government entities would keep their blueprints around for future need.

On a side note, It would be interesting to see what kind of weight/cost savings NASA can achieve by using modern materials and fabrication methods on the F1 engines. I'd imagine that replacing a large part of the steel with carbon fiber or composites would shave considerable weight.

Engineers removed components from an F-1 engine in storage at MSFC, as well as from another in "pristine" condition at the Smithsonian National Air and Space Museum in Washington, and then laser-scanned them using a structured light 3D scanner. Once this had been done, new gas generator parts were fabricated from the scans.

This part puzzled me. I always assumed there was a filing cabinet somewhere, at NASA HQ or elsewhere, with the blueprints for all their past constructions, so it's weird to me that the engineers here had to measure the parts needed in order to manufacture replacements. After the inevitable apocalypse/rapture the left behind will rely on a repository of instructions to rebuild machines common to us today, tractors, bulldozers, gas-generator cycle rocket engines. Is that not going to happen?

NASA put most of the technology into inadequate storage. North American Rockwell the contractor dumped all of their copies long ago. Probably was faster to directly measure it than to find copies of copies of the original docs. NASA didn't have enough money to properly store anything even the original Apollo 11 video tapes were either lost or recorded over.

Engineers removed components from an F-1 engine in storage at MSFC, as well as from another in "pristine" condition at the Smithsonian National Air and Space Museum in Washington, and then laser-scanned them using a structured light 3D scanner. Once this had been done, new gas generator parts were fabricated from the scans.

This part puzzled me. I always assumed there was a filing cabinet somewhere, at NASA HQ or elsewhere, with the blueprints for all their past constructions, so it's weird to me that the engineers here had to measure the parts needed in order to manufacture replacements. After the inevitable apocalypse/rapture the left behind will rely on a repository of instructions to rebuild machines common to us today, tractors, bulldozers, gas-generator cycle rocket engines. Is that not going to happen?

It's probably a lot easier to go from laser scans of the actual parts into a 3d file than it is to translate everything from line drawings.

Pretty fricken remarkable isn't it? Designed 50 years ago, no less. Saturn V happens to be the only booster in history with a flawless launch record. Although it was with a bit of luck as they had their problems, as tigas outlined. They had issues with POGO oscillations on practically every mission.

Define "history." I'm sure I could find at least several other vehicles with much shorter service records without a failure to their record. In fact, I can think of one off the top of my head: SpaceX's Falcon 9 is at 4 successful launches without failure, and counting.

That giant flame is created by the part of the engine the just drives the pumps? Thats insane

Wecome to rocketry. Insanely powerful rocket engines require insanely powerful pumps to keep them fed, and if you want it in a package that's small enough to be useful, it's also going to have insane power density, aka, a fuckoff huge flaming exhaust.

NASA put most of the technology into inadequate storage. North American Rockwell the contractor dumped all of their copies long ago. Probably was faster to directly measure it than to find copies of copies of the original docs. NASA didn't have enough money to properly store anything even the original Apollo 11 video tapes were either lost or recorded over.

Money, and I'm not certain people back then really had the sense of, "history in the making, let's preserve it".

NASA put most of the technology into inadequate storage. North American Rockwell the contractor dumped all of their copies long ago. Probably was faster to directly measure it than to find copies of copies of the original docs. NASA didn't have enough money to properly store anything even the original Apollo 11 video tapes were either lost or recorded over.

Money, and I'm not certain people back then really had the sense of, "history in the making, let's preserve it".

Yeah, they were expecting new F1 engines and Saturn V upgrades to come down the line in short order, not for Congress to pull the plug just as everything was getting started.

If you read the article I posted, Rocketdyne even recorded interviews with the lead technicians to pick their brains on the stuff they had found out while building and developing the engine (anecdotes, blind alleys, serendipity, etc.). But restarting production of the F-1A would cost half a billion dollars just the same.

It's probably a lot easier to go from laser scans of the actual parts into a 3d file than it is to translate everything from line drawings.

This is the real answer. The "complete" set of "blueprints" is on file at Marshall. There's fiche and paper of everything, though I put "complete" in fingerquotes because as has been noted, the Saturn V wasn't a single entity but rather a complex system of systems, all built by different contractors.

The problem with rebuilding engine components from the plans is that 1960s-era documentation that talks in terms of 1960s standard parts doesn't necessarily tell you how to build a complex system like a rocket. Rather than deal with potentially inexact documentation, you can just pull parts from an existing thing and measure & dupe them.

That giant flame is created by the part of the engine the just drives the pumps? Thats insane

Wecome to rocketry. Insanely powerful rocket engines require insanely powerful pumps to keep them fed, and if you want it in a package that's small enough to be useful, it's also going to have insane power density, aka, a fuckoff huge flaming exhaust.

And yet by modern standards, it's not even that powerful a turbo pump. The one in the RD-171 is something like 5x more powerful which allows it to operate at a much higher chamber pressure with a consequent increase in Isp.

The F1 was impressive in terms of sheer size and thrust but I get the impression that in many ways it was pretty crude and was something of a brute force solution. Given the race to make Apollo work, that was probably the right choice rather than trying to create a more efficient and sophisticated engine using staged combustion and higher pressures.

It's remarkable the job the engineers did back then with technology now that appears stone-aged. Yet they managed to put man on the moon, rescue men going to the moon from certain death and other technological marvels (SR-71 Blackbird) that still have not been surpassed almost 50 years later in some cases.

Pratt&Whitney-Rocketdyne seems to be also seriously looking at the F1, as an engine for advanced liquid-fueled boosters for the Block 1b and later versions of the SLS. They reckon that by using two of them per booster, four in total, to replace their shuttle-derived five-segment SRBs, they can deliver about 15% more payload more reliably and less expensively than other options, perhaps even removing the need for a Block 2 SLS design. Of course, ATK has their own advanced booster plans for their solid booster technology, so time will tell.

Call me cynical, but I think that any company going up against ATK in a rocketry competition will lose. And I don't particularly think ATK has the better product, either.

This part puzzled me. I always assumed there was a filing cabinet somewhere, at NASA HQ or elsewhere, with the blueprints for all their past constructions, so it's weird to me that the engineers here had to measure the parts needed in order to manufacture replacements.

It's probably a lot easier to go from laser scans of the actual parts into a 3d file than it is to translate everything from line drawings.

I agree it's probably easier to 3D scan to parts. Also, no matter how good the documentation process was, there are bound to be some changes to the design that didn't get properly updated in the paper schematics. Also there could be manufacturing tolerance differences that also aren't in the spec. It's much better to measure the actual part since the machined parts used to build the parts aren't around anymore.